Formation fluids including oil and gas produced at a wellhead are conveyed through flow lines to remote gathering stations. It is conventional practice to use safety valves which are responsive to certain changes in operating conditions to automatically shut off flow at the surface and below the wellhead at the onset of unusual or unscheduled operating conditions. For example, conventional oil and gas gathering systems include surface and subsurface safety valves which are designed to automatically close in the event of fluctuations either above or below predetermined settings, such as high and low liquid levels, high and low temperatures and electrical power loss. Also, catastrophic failures may occur in which the flow lines and wellhead equipment are destroyed by explosion, fire and the like. Offshore production wells must sometimes be shut off quickly to avoid storm damage. In such situations, it is imperative that well flow be terminated to avoid waste and pollution.